IV. Conduction of AP

Intro

• Signal propagates as series of APs along axon

• Voltage shifts in one region -> triggers

• Na+ channels further down

• Areas behind in refractory period 

• Unidirectional signal

• Artificially stimulate axon center

  • AP in two directions

Continuous Conduction

• Occurs in unmyelinated axons (grey matter)

• Smooth wave of depolarization 

• No insulation/ lipid presence, slow response 

• Every spot depolarizes, repolarizes

Saltatory conduction

• Occurs in myelinated axons (white matter)

• Requires myelin sheath: fatty insulation for AP, rich in myelin

• Made by oligodendrocytes (CNS) and Schwann cells (PNS)

• Internodes: regions covered my myelin- no depolarization 

• Nodes of ranvier: no myelin- lots of Na+, K+ channels

  • Depolarization only occurs at nodes

  • Signal jumps from node to node

  • >50x faster than unmyelinated 

  • reflexes

  • more E efficient

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